Announcement (2017-05-07): www.ruby-forum.com is now read-only since I
unfortunately do not have the time to support and maintain the forum any
more. Please see rubyonrails.org/community and ruby-lang.org/en/community
for other Rails- und Ruby-related community platforms.

Sounds like you're not running Dev.bat. Before doing anything with
IronRuby (when you get it from the git repo), please run
Merlin/Main/Languages/Ruby/Scripts/Dev.bat. That will make sure things
are all set up properly. To make this easy, just create a ironruby.bat
file somewhere which calls Dev.bat. I even add that as the first
shortcut in my quicklaunch toolbar so WIN+1 will launch a dev.bat
cmd.exe window.
~js

If you have RUBYOPTS set to "-rubygems" (as is done by default by the
MRI one-click installer), RubyGems will get first shot at finding
"mspec" and will look at installed gems before looking at $LOAD_PATH.
That could also be the issue. Just using the different version of
mspec.bat may not fix the issue as it just runs the first "ruby.exe" it
finds on the path, and could still get tripped up over the "-rubygems"
issue...
Jim, how different are the two versions of mspec supposed to be? Do you
know what the RubySpec team's plan is to unify them? Do we know why the
gem will not work, and is there a bug to track the issue?